What are the functions of the LEFT JOIN and RIGHT JOIN in SQL?

LEFT JOIN returns all records from the left table and matched records from the right table, while RIGHT JOIN does the opposite.

In SQL, the LEFT JOIN and RIGHT JOIN functions are used to combine rows from two or more tables based on a related column between them. These functions are part of the broader category of SQL JOIN operations, which also include INNER JOIN and FULL JOIN. The LEFT JOIN function returns all the records from the left table (table1), and the matched records from the right table (table2). If there is no match, the result is NULL on the right side.

For example, if you have two tables, Customers and Orders, and you want to list all customers and any orders they might have, you would use a LEFT JOIN. This would return all customers, and any matching order information. If a customer has no orders, that customer would still be listed, but the order information would be NULL.

On the other hand, the RIGHT JOIN function returns all the records from the right table (table2), and the matched records from the left table (table1). If there is no match, the result is NULL on the left side.

Using the same Customers and Orders example, if you wanted to list all orders and the customer information for those orders, you would use a RIGHT JOIN. This would return all orders, and any matching customer information. If an order has no matching customer, that order would still be listed, but the customer information would be NULL.

In essence, the choice between using a LEFT JOIN or a RIGHT JOIN depends on which table you want to have all records returned from, and which table's records you want returned only where there is a matching record in the first table. It's important to note that not all database systems support RIGHT JOIN, but you can always achieve the same result by switching the order of the tables and using a LEFT JOIN.